One challenge that a producer of agricultural crops faces when attempting to properly adjust the operating parameters of his planting equipment is the varying soil conditions frequently encountered during planting operations. Varying soil conditions result from differing soil types (sand, clay, or silt), differences in soil moisture, drainage and tillage practices or conditions throughout the field. In addition to varying soil conditions, different operating speeds may require different adjustments to be made to the equipment.
One operating parameter over which the operator has the most control for adjusting to varying soil conditions is the downforce applied to the planter row unit. There are two problems associated with improper downforce being applied to the planter row unit. The first problem is that excess downforce results in too much weight being carried by the depth regulating member (i.e., depth gauge wheels, skis, skids, runners etc.). Excessive weight can compact the soil surrounding the furrow and thereby inhibit proper development and growth of the roots and plant. Excessive downforce can also result in a planting depth that is too great with some types of furrow openers. The second problem is that insufficient downforce can result in a shallow furrow which can also detrimentally effect the yield as the seed may not be deep enough to have adequate moisture for proper germination.
It is generally understood that the total downforce acting on the row unit consists of the dead weight of the row unit plus the live weight of seed and/or insecticide carried upon the row unit, plus any supplemental downforce applied through the parallel arm linkage. Of the total down force for the row unit, the majority is used in forcing the opener disk(s) into the soil to the desired seeding depth. The remainder of the total down force is carried by the depth gauge wheels.
Several attempts have been made to develop a control system which measures or senses the load on the gauge wheels. One such system is disclosed in European patent EP0372901 to Baker (the “Baker '901 patent”) which utilizes a displacement transducer or load cell to measure the average load on the gauge wheels over a period of time.
Another system is disclosed in U.S. Pat. No. 6,389,999 to Duello (the “Duello '999 patent) which discloses the use of a strain gauge or other sensor for measuring the average load on the gauge wheels over a period of time. The disclosure of the Duello '999 patent at least acknowledges that there will be frequent load shifts experienced by the load sensors. However, Duello '999 suggests that the loads signals should be filtered in order to avoid “constant, minute responses that may task and overwork the system.” It should be understood, that when a signal is filtered as suggested by Duello '999, the resultant data trace will identify only the average value of the signal over the given time interval as opposed to identifying the actual detected signal peaks and valleys. The Duello '999 patent also suggests that some “change limit” must be exceeded before action is taken. Although it is unclear from the Duello specification, it is assumed that this change limit is a predetermined amount by which the load must change relative to the average before any action is to be taken.
Yet another system is disclosed in U.S. Pat. No. 6,701,857 to Jensen (the “Jenson '857 patent”). Jenson '857 discloses a depth control device that also measures the load on the gauge wheels where “readings are averaged and sampled every few seconds so as not to create an erratic reading.” Jenson '857 speaks of a desired or predetermined load value (target load) input by the operator. A control algorithm regulates the downforce in an attempt to ensure the average downforce matches the target load as closely as possible.
While each of the forgoing systems may perform their intended purpose, it should be recognized that not all soil conditions result in the same type of gauge wheel loadings. If the operator is required to select a target load, the selected target load may be too great (resulting in soil compaction) or too little (resulting in shallow furrows) depending on the changing soil conditions. For example, highly tilled soil will be very uniform as well as very compactable, resulting in very uniform load upon the gauge wheels throughout the field. By contrast, in no till or minimum tillage systems, the soil structure will vary dramatically throughout the field. FIG. 2 illustrates the load signal generated from actual planting conditions in a field which was highly tilled and had a uniform soil type. The average load was approximately 100 pounds and the signal deviated little from this value, never falling lower than 85 pounds or rising greater than 115 pounds. FIG. 3 illustrates the load signal from a minimum tillage field where the load was varying dramatically. The average load was approximately 150 pounds but dropped nearly to zero and rose as high as 300 pounds at times. These two scenarios show the different characteristics of gauge wheel loadings that prevent an operator from making the best determination of downforce setting based solely on average load alone. Thus, the aforementioned systems fail to provide the necessary information to the operator or an automatic control actuator to minimize excess soil compaction while at the same time avoiding loss of proper furrow depth.
The proper downforce for any given planting condition should be that amount of downforce required to maintain the desired furrow depth without imparting excessive compaction to the soil surrounding the furrow. Balancing these two criteria is difficult because, as explained above, minimizing compaction will tend to create a loss of furrow depth, whereas minimizing loss of furrow depth will tend to increase compaction. Accordingly, there is a need for a system and method for determining the proper downforce for planter row units that will ensure desired furrow depth while minimizing soil compaction.